don't forget a gallon of water or engine coolant
and if you have a generator, i'd suggest a charger or better yet a 100 amp charger/starter. IT's sometimes difficult to convince a stranger to give ya a jump start.
IF you have air brakes, i'd definately go for the air driven impact wrench. All of the fittings on your air tank under the bus are standard NPT (national pipe thread) you can go to home depot and buy all the fittings for about 10 bucks.
Bring some wrenches, especially important is the wrench that fits the nut on top of the injector to bleed the air out of the system (if it's a diesel)
Go-JO and paper towels so you can get cleaned up in the event you have to work on the bus
an extra 5 or 10 gallons of fuel isn't a bad idea if you have a place to store it
Quis custodiet ipsos custodes (who will watch the watchmen?)